The present invention relates to a cutting tool for machining by chip removal, which cutting tool comprises a substrate of cemented carbide, cermet, ceramics, cubic boron nitride based material, or high speed steel, and a hard and wear resistant refractory coating of which at least one layer of the coating comprises a cubic c-(Me,Si,)N-phase without a co-existing amorphous phase.
TiN has been widely used as a hard layer on cutting tools, but its poor oxidation resistance at temperatures above 500° C. has created an interest in ternary or quaternary compounds, e.g., Ti—Al—N and Ti—Cr—Al—N.
More complex quaternaries, e.g., Ti—Al—Si—N have been reported and described as super hard (H>45) GPa due to a two phase structure consisting of a crystalline phase of a NaCl-type in combination with amorphous Si3N4 or SiNx. These coating materials show an improved oxidation resistance and improved performance in machining of hardened steels.
However, material based on an amorphous phase tends to plastically deform by grain boundary sliding at elevated temperature which is why optimum performance is not obtained by that solution.